HILL: GEOLOGY OF JAMAICA. 117 



molluscan species of the adjacent continental borders found habitat in 

 the littoral waters of the island prior to the late (Jligocene (Bowden) 

 epoch, when the bottom of the region was sufficiently elevated to per- 

 mit the migration of shallow water species over wide areas of the 

 tropical seas and to connect the Jamaican littoral fauna with that of 

 the mainland. Forms which abound in the preceding epochs, especially 

 the corals and Foraminifera, are those adapted to wide oceanic migration. 

 These conditions have produced in these earlier faunas a peculiar mix- 

 ture of genera, comprising oceanic species and a few littoral mollusca 

 which had found accidental foothold and acquired peculiar characters 

 through long isolation, — the whole making a faunal assemblage quite 

 foreign to those known in other typical areas of the world upon which 

 stratigraphic and age classifications have been founded, although re- 

 taining generic criteria sufficient for positive age determination. Pale- 

 ontologists, unaware of these conditions, have naturally failed to obtain 

 in the collections from the island a correct impression of the strati- 

 graphic significance of its fossils. 



In view of the confused condition of current published conceptions 

 of the paleontology of Jamaica above set forth, it will be impossible in 

 the present chapter to straighten out the confused synonomy of species, 

 a task which must be left to other specialists. Our principal endeavor 

 will be to point out the true stratigraphic position of the material 

 hitherto described, thereby making it of geologic as well as biologic 

 value, and then, by aid of the larger amount of new material collected 

 by us, present some deductions which may be of service to those who 

 in the future undertake the special task of further advancing the 

 paleontology of Jamaica. 



Cretaceous. 

 Blue Mountain Series. Lower Division. 



From the occasional limestones and marl beds occurring in the vast 

 thickness of tuffs and conglomerates of the lower division of the Blue 

 Mountains, the following fossils have been collected, most of which have 

 a decided Cretaceous facies. 



Foraminifera ; Rotalia or Pidvinulina ^ ; ^Orbitoides (T) ^ ; Ellipsac- 

 tina^; *Nummulites (1).^ 



Corals : Cladocora jamaicaensis, Yaughan ; *Diploria conferticostata, 



1 Identified by Tl. M. Bagg. Collected by Robert T. Hill. 



2 Identified by Woodward. Collected by Jamaican Surveys. 



